Optical multi-point measurement of the acoustic particle velocity in a superposed flow using a spectroscopic laser technique
Optical multi-point measurement of the acoustic particle velocity in a superposed flow using a spectroscopic laser technique
复制标题
使用光谱激光技术对叠加流中的声粒子速度进行光学多点测量
DOI：
10.1088/0957-0233/23/8/085306
复制
发表时间：
2012
影响因子：
2.4
通讯作者：
J. Czarske
中科院分区：
文献类型：
--
作者：
D. Haufe;Raimund Schlüßler;A. Fischer;L. Büttner;J. Czarske
喷气发动机的降噪需要优化吸声器，例如偏流衬套。为了提高效率，需要加深对衬里声流相互作用的理解。因此，声粒子速度和流速的同时测量是不可避免的。由于声粒子速度通常小于 100 mm s-1 并且流速约为 100 m s-1，因此此处需要最小 103 的高动态范围和 1 mm s-1 的低测量不确定度。为了在不违反奈奎斯特-香农采样定理的情况下解析高达 20 kHz 的可听频率范围内的声粒子速度，还需要超过 40 kHz 的测量速率。调频多普勒全局测速 (FM-DGV) 满足了所有这些要求，本文对此进行了论证。在同时多点测量中以 50 kHz 的测量速率解析了多个声音频率，结果与理论非常吻合。测量持续时间为 1 秒，测量不确定度平均为 4 mm s−1，并且可以通过增加测量持续时间进一步降低。此外，结果表明，可以使用 FM-DGV 测量流动中的声粒子速度，提供 4 × 103 的高动态范围。
Noise reduction in jet engines requires the optimization of sound absorbers, for example, bias-flow liners. To increase their efficiency, an enhanced understanding of the sound–flow interaction at liners is needed. Therefore, the simultaneous measurement of the acoustic particle velocity and the flow velocity is inevitable. Since the acoustic particle velocity is typically smaller than 100 mm s−1 and the flow velocity is about 100 m s−1, a high dynamic range of minimum 103 and a low measurement uncertainty of 1 mm s−1 are required here. To resolve the acoustic particle velocity in the audible frequency range up to 20 kHz without violating the Nyquist–Shannon sampling theorem, a measurement rate of more than 40 kHz is also demanded. Doppler global velocimetry with frequency modulation (FM-DGV) fulfils each of these requirements, which is demonstrated in this paper. Multiple sound frequencies were resolved with a measurement rate of 50 kHz at a simultaneous multi-point measurement showing excellent agreement with the theory. The measurement uncertainty of 4 mm s−1 on average was achieved for a measurement duration of 1 s and can be reduced further by increasing the measurement duration. Furthermore, it is shown that the acoustic particle velocity can be measured in a flow with FM-DGV providing a high dynamic range of 4 × 103.